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Question

Difficulty: HardContrast and Reversal Clues

Although deep-sea hydrothermal vent ecosystems were long presumed to be remarkably ________ due to their total isolation from sunlight, recent oceanographic surveys have revealed surprisingly dynamic food webs that fluctuate in response to upper-ocean biological cycles. Which of the following words best completes the blank in the passage?

  1. invariantAnswer
  2. B
    vibrant
  3. C
    ephemeral
  4. D
    pristine
  5. E
    precarious

Answer

The word 'invariant' best completes the blank.
The sentence begins with the concessionary pivot 'Although', indicating that the initial presumption about hydrothermal vent ecosystems contrasts directly with recent findings. Since recent oceanographic surveys show these ecosystems possess 'surprisingly dynamic' food webs, the blank requires a word that means static, unchanging, or fixed. The word 'invariant' precisely fulfills this requirement by denoting an unvarying state.

Step-by-Step Solution

1
Identify structural transition signals and contrast pivots in the passage.
The opening word 'Although' signals a structural contrast between the initial presumption regarding deep-sea hydrothermal vent ecosystems and the subsequent empirical findings.
Contrast pivots dictate that the missing word must convey a semantic meaning opposite to the idea presented in the main clause.
2
Analyze the context of the main clause to determine the target semantic valence.
The main clause notes that recent surveys revealed 'surprisingly dynamic food webs.'
The word in the blank must contrast directly with 'dynamic' (active, fluctuating, or changing).
3
Evaluate the choices to find the word denoting a static or unvarying state.
'Invariant' means static or unchanging, perfectly contrasting with 'dynamic.'
'Invariant' satisfies the required semantic reversal established by the concessionary pivot 'Although.'

Key Concept

Identifying structural contrast pivots to deduce opposite semantic meanings in Text Completion questions.
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Topics

Contrast and Reversal Clues

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